ISSN 10227954, Russian Journal of Genetics, 2011, Vol. 47, No. 5, pp. 564–570. © Pleiades Publishing, Inc., 2011.
Original Russian Text © N.A. Yakovin, I.A. Fesenko, A.V. Isachkin, G.I. Karlov, 2011, published in Genetika, 2011, Vol. 47, No. 5, pp. 643–650.
) is one of the leading cultivated
fruit trees of the temperate regions. It ranks second
after apple tree as a deciduous culture in commercial
fruit production (over 20 million tons per year) .
Pear has been cultivated for more than 2 000 years .
consists of about 60 species, which
are usually subdivided into two sections,
. The most accurate classifying character is the
presence of deciduous fruit calyx in the species of the
, while the species of the section
lack this character. The species of section
in Europe, Northern Africa, West and Central Asia.
, growing in the Russian Far
East and in Northeast China is also attributed to this
section. Among numerous pear species, only
L. (common pear) and
pear or Nashi) are commercially important. In Russia,
a special role is played by the cultivars representing the
first and following generations from the cross between
common pear and Ussurian pear (
latter species is the source of resistance to frost and
scab . Most part of the assortment of temperate
region, as well as the whole assortment of the Urals
and Siberia are represented by the cultivars having
as one of the ancestors. The State Regis
ter of Breeding Achievements of the Russian Federa
tion currently includes a total of 123 pear cultivars.
Traditionally, genetic diversity of pear cultivars and
species is analyzed using morphological traits  and
polymorphism of storage proteins . Unfortunately,
both of these approaches are limited by the number of
morphological traits available for analysis. In addition,
morphological traits are subject to modifications. At
present, these issues in many cases are solved using
molecular markers constructed based on the nucle
otide DNA markers sequence polymorphism.
In many cultivated plants DNA markers were suc
cessfully used for analysis of intercultivar polymor
phism and for establishing relationships between them
. In pear, these investigations were performed using
different types of DNA markers, including RAPD,
AFLP , ISSR , and SSR [10–13]. Furthermore,
it was demonstrated that SSR markers were most
effective and reliable for evaluation of intercultivar
polymorphism and cultivar certification [13–17].
The SSR (simple sequence repeat) markers are
based on microsatellite polymorphism. Microsatellites
are genome regions consisting of highly repetitive short
(1–6 bp) DNA sequences . These DNA regions are
highly polymorphic and thus convenient for evaluation
of the relationships between genotypes. SSR markers are
characterized by high reproducibility of the results and
codominant mode of inheritance .
The present study was focused on molecular
genetic analysis of pear cultivars and species per
formed using SSR markers. The degree of relatedness
between pear cultivars of Russian and Western Euro
pean bred was established.
MATERIALS AND METHODS
The experiments were carried out
using 52 pear accessions from the collection of the
Michurin Garden, Timiryazev Russian State Agrarian
University (Table 1). Among these, 46 were cultivars of
Polymorphism of Microsatellite Loci in Cultivars and Species
of Pear (
N. A. Yakovin, I. A. Fesenko, A. V. Isachkin, and G. I. Karlov
Center for Molecular Biotechnology, Russian State Agrarian University–MTAA, Moscow, 127550 Russia
Received June 9, 2010
—Using five SSR markers, polymorphism of microsatellite loci was examined in 46 cultivars and five
species of pear (
). Most of the accessions
examined showed the presence of unique allele sets. The degree of relationship between Russian and Western
European pear cultivar was established. It was demonstrated that
and its first generation progeny
were genetically distant from typical cultivars of
, as well as from the
hybrids of later generations. SSR estimates of the cultivar relatedness were shown to correlate with the corre
sponding pedigreebased estimates. A number of SSR alleles specific to
were identified. Based
on the analysis of microsatellite loci, the allelic composition was determined for each cultivar examined.
These data can serve as a molecular certificate of the cultivar.